Bárbara A. Vento

Reevaluación de las Biozonas de Tetragraptus Phyllograptoides y T. akzharensis (Ordovícico Inferior, Floiano) de la Cordillera Oriental Argentina

Abstract. REEVALUATION OF TETRAGRAPTUS PHYLLOGRAPTOIDES AND T. AKZHARENSIS BIOZONES (LOWER ORDO-VICIAN, FLOIAN) FROM THE CORDILLERA ORIENTAL ARGENTINA. This paper presents new accuracies and correlations of the Lower Ordovician (Floian) biostratigraphic scheme of the Cordillera Oriental. The Tetragraptus phyllograptoides and T. akzharensis biozones are reevaluated based on graptolite records from the lower levels of the Acoite Formation, outcropping in the Quebrada de Quinilicán (Sierra de Aguilar). The stratigraphic range of the characteristic taxa is discussed and compared with that observed in Los Colorados area. In the Tetragraptus phyllograptoides Biozone, it is worth mentioning the presence of Tetragraptus approximatus (Nicholson), Tetragraptus sp., Baltograptus geometricus (Törnquist), Cymatograptus demissus (Törnquist) and C. rigoletto (Maletz, Rushton and Lindholm) in addition to the index species. Tetragraptus amii (Elles y Wood), Cymatograptus protobalticus (Monsen), C. balticus (Tullberg) and Paradelograptus sp. appear in the lower part of the T. akzharensis Biozone, whereas Baltograptus vacillans (Tullberg), Corymbograptus v-fractus tullbergi (Monsen), Trichograptus dilaceratus (Herrmann), Expansograptus latus (Hall), E. holmi (Törnquist), E. constrictus (Hall), Acrograptus gracilis (Törnquist), and A. filiformis (Tullberg) are recorded in the upper portion of the same biozone. The regional correlation of both biozones is corroborated on the western margin of the Cordillera Oriental. The possible subdivision of the T. akzharensis Biozone is commented, according to the biostratigraphic scheme recently proposed for Scandinavia, and a more accurate intercontinental correlation of Northwestern Argentina Floian levels is proposed. In addition, the paleoecological implications of some studied taxa and the paleobiogeographical relationships between Northwestern Argentina and other Gondwanan regions are discussed, and the strong affinity with Baltoscandinavia during the Lower Ordovician is validated.

Paleoecological and paleobiogeographic considerations of Ordovician graptolites from the Cordillera Oriental, Jujuy Province, Argentina

We analyse new paleoecological data from South American graptolite records to understand the patterns that influence the space-tempo distribution of the group. A cluster analysis including taxa from the Baltograptus cf. B. deflexus and Didymograptellus bifidus Zones is carried out to evaluate the paleogeographic relationships between north-western Argentina and the other regions in the world. Three different biofacies were recognised in the Acoite Formation. The first biofacies takes place in the lower part of the unit, corresponding to pelitic levels (Tetragraptus phyllograptoides and Tetragraptus akzharensis Zones), and it is represented by pandemic forms. The other two biofacies belong to the endemic or neritic shallow water environments, and develop in deposits corresponding to the middle part of the Acoite Formation (bottom of the Baltograptus cf. B. deflexus Zone) in the Sierra de Aguilar, and in the upper half of the unit exposed in the Los Colorados area (D. bifidus Zone), respectively. The statistical analysis highlight the paleobiogeographic relationship between north-western Argentina and south-western China during the middle-upper Floian (Baltograptus cf. B. deflexus and D. bifidus Zones), and it supports the hypothesis that during the Early Ordovician north-western Argentina was located in the middle to high latitudes, included in the cold water faunal realm.

Urban forest of Mendoza (Argentina): the role of Morus alba (Moraceae) in carbon storage

ABSTRACT Carbon dioxide emissions have partially been attributed to urban areas. Nevertheless, cities provide valuable ecosystem services such as carbon storage. The aim of this study is to estimate the carbon storage of Morus alba trees as a dominant species in the urban forest of Mendoza city. A stratified random sampling was selected for both urban and suburban areas. Trees were analyzed considering the following parts: stem, primary and secondary branches, and leaves. Underground dry matter was also estimated. Tree dry matter was distributed as follows: crown 53%, stem 25%, root 20%, and leaf 2%. Considering the total M. alba coverage, the urban area accumulates 24,208 tonnes and the suburban area 43,000 tonnes of carbon, from which 544.6 tonnes (1998.6 t CO2) and 1123.3 tonnes (4,118.8 t CO2) are annually removed by leaves. These quantities are relevant considering the 13,000 t/year of CO released to the atmosphere in Mendoza city. The accumulated carbon values evidence the importance of preservation and conservation tasks that are essential in the management of the urban forest located in drylands.

Mineral contents in leaves of Morus alba L. (Moraceae) and Platanus hispanica Miller (Platanaceae) from the urban forests of central-western area of Argentina.

Abstract The returning of mineral contents and organic matter to the soil as litterfall is one of the most essential ecological process that contributes to the nutrient cycles and provides enough nutrients to plants for a healthy growth. The fallen leaves from urban forests of the cities of San Juan and Mendoza, Argentina are frequently collected especially during the autumn season with a loss of great quantity of litterfall every year. High amounts of nutrients and organic matter are exported from the urban ecosystem without completing the mineral nutrient cycle. The aim of this work is to evaluate the variation in foliar mineral and organic matter contents along seasons (spring, summer and autumn) for the two most abundant non-native species: Morus alba and Platanus hispanica located in the urban forests of the central-western part of Argentina, and the effect of the periodical leaf removal in urban areas. Differences in mineral and organic matter contents were found along the seasons. Foliar concentration losses follow the order of magnitude: N > Mg > P>K > Na. This research is a contribution to a more adequate understanding of the urban ecosystem patterns and dynamics, and it means to be helpful in the management and conservation practices of urban ecosystems.

Testing phylogenetic relationships of Floian (Ordovician) Graptolite records from Argentina through Cladistic analysis

Abstract. The analysis of two-stiped dichograptids, largely of baltograptid and expansograptid taxa of the family Didymograptidae from the Floian of northwestern Argentina, provides insight into the evolutionary relationships of this group. The important proximal end characters clearly cluster the baltograptids with the derived genera Didymograptus and Aulograptus. One of the analyses provides the information that the genera Cymatograptus and Expansograptus share a common ancestor but are not closely related to the two-stiped Kiaerograptus and related taxa. Likewise, with the exception of some controversial taxa, the families Tetragraptidae and Didymograptidae can be readily differentiated, supporting previous interpretations that they represent monophyletic clades. Although the present analyses are poorly supported, they provide hypotheses that could be further tested based on new data on isolated dichograptid taxa based on isolated or relief-preserved material.

Análisis Morfométrico de Especies del Género Baltograptus (Graptolithina) en el Ordovícico Temprano de la Cordillera Oriental, Argentina

Resumen. La morfometría aplicada a graptolitos constituye una herramienta poco desarrollada en la actualidad. Este tipo de análisis se realiza por primera vez en Argentina, con el objetivo de brindar un soporte adicional para la clasificación sistemática a nivel de especie, de ejemplares problemáticos del género Baltograptus. El material proviene de la Cordillera Oriental, asignado previamente a las especies B. turgidus (Lee) y B. kunmingensis (Ni), e incluido sucesivamente en grupos informales. Estas especies fueron definidas originalmente en China, junto a muchas otras difícilmente diferenciables, que se caracterizan por presentar tubarios robustos de carácter deflexo, con rápido ensanchamiento de sus estipes. Material adicional de características similares, que fuera asignado anteriormente a Baltograptus bolivianus (Finney y Branisa), se incluye también en este análisis. A partir de la cuantificación de las variables morfométricas se llevó a cabo un análisis de tipo exploratorio (análisis de componentes principales), seguido del análisis de agrupamiento y del posterior análisis discriminante. Como resultado, el material se separa en tres agrupamientos diferentes, que corresponden claramente a las tres especies en discusión. Si bien las variables correspondientes al extremo proximal del tubario influyen en la discriminación de los grupos resultantes, aquellas correspondientes al resto de la colonia ejercen mayor preponderancia en la separación a nivel de especie. El análisis de los parámetros morfométricos seleccionados constituye una base necesaria de comparación con trabajos similares que se encuentran en desarrollo actualmente en China, donde estas y otras especies semejantes fueron originalmente descriptas. Abstract. MORPHOMETRIC ANALYSIS OF EARLY ORDOVICIAN BALTOGRAPTUS SPECIES FROM THE CORDILLERA ORIENTAL, ARGENTINA. The application of morphometric techniques to graptolites is still under development. This kind of analysis is carried out for the first time in Argentina to give additional support to the systematic classification at species level for problematic specimens of the genus Baltograptus. The material comes from the Cordillera Oriental, and was previously assigned to B. turgidus (Lee) and B. kunmingensis (Ni) and subsequently included in informal groups. These species were originally described in China, along with many other species of difficult differentiation, which are characterized by a robust and deflexed tubarium with a rapid widening of the stipes. Additional similar material previously assigned to Baltograptus bolivianus (Finney and Branisa), is included in the analysis. An exploratory analysis (principal component analysis) was carried out, based on the quantification of the morphometric variables. It was followed by a cluster analysis with a subsequent discriminant analysis. The results showed that the specimens are separated into three groups, clearly corresponding to the discussed species. The variables of the distal part of the tubarium appear to have more influence in the separation of species. However, some variables corresponding to the proximal end also influence the resulting group discrimination. The analysis of the selected morphometric variables constitutes a foundation for comparison with similar studies, currently in progress in China, where the analyzed species as well as other related species, were originally described.

ANÁLISIS MORFOMÉTRICO DE ESPECIES DEL GÉNERO BALTOGRAPTUS, ORDOVÍCICO TEMPRANO, CORDILLERA ORIENTAL, ARGENTINA

La morfometria aplicada a graptolitos, constituye una herramienta poco desarrollada en la actualidad. Este tipo de analisis se realiza por primera vez en Argentina, con el objetivo de brindar un soporte adicional para la clasificacion sistematica a nivel de especie, de ejemplares problematicos del genero Baltograptus. El material proviene de la Cordillera Oriental Argentina y fue asignado previamente a las especies B. turgidus (Lee) y B. kunmingensis (Ni), e incluido sucesivamente en grupos informales, como el de B. turgidus. Estas especies fueron definidas originalmente en China, junto a muchas otras dificilmente diferenciables, que se caracterizan por presentar tubarios robustos de caracter deflexo, con rapido ensanchamiento de sus estipes. Material adicional de caracteristicas similares, que fuera asignado anteriormente a Baltograptus bolivianus (Finney y Branisa), debido a la presencia de pliegues protecales, se incluye tambien en este analisis. A partir de la cuantificacion de las variables morfometricas (longitud de la sicula, ancho de la sicula, ancho proximal del estipe, ancho distal del estipe, ancho maximo del estipe y numero de tecas en 10 mm) se llevo a cabo un analisis de tipo exploratorio (analisis de componentes principales), seguido del analisis de conglomerados y del posterior analisis discriminante. Como resultado, el material se separa en tres conglomerados diferentes, que corresponden claramente a las tres especies en discusion. Si bien, las variables correspondientes al extremo proximal del tubario influyen en la discriminacion de los grupos resultantes, aquellas correspondientes al resto de la colonia ejercen mayor preponderancia en la separacion a nivel de especie. El analisis de los parametros morfometricos seleccionados constituye una base necesaria de comparacion con trabajos similares que se encuentran en desarrollo actualmente en China, donde estas y otras especies semejantes fueron originalmente descriptas.